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Factors Affecting Small Intestinal Carbohydrate Assimilation in Beef Cattle
D.L. Harmon, K.R. McLeod
Department of Animal and Food Sciences
The complexity of ruminant digestion makes it diffcult to determine how dietary ingredients are utilized. This project evaluates nutrient utilization in the animal and by the animal to determine how growth and nutrient utilization interact.
2011 Project Description
The objective of this study was to compare nitrogen metabolism and urea kinetics between diets containing either rapidly degrading or slow degrading non protein nitrogen (NPN) at varying levels of degradable intake protein (DIP). NPN source was slow release urea (Optigen II, OPT) or feed grade urea fed at 89, 100 or 114% of calculated DIP requirements.
Eight Holstein steers (209 kg) implanted with Synovex Plus were used in a replicated 4 x 4 Latin square. Periods were 27 d, with 19 d adaptation followed by 7 d of urine and fecal collection and 1 d of blood sampling. Continuous (78h) intravenous infusion of 15N15N-urea allowed estimation of urea kinetics. Dry matter intake was not different between treatments (7.2 kg/d).
Increasing DIP had a tendency to increase dry matter digestibility (DMD) for both Urea and OPT. Urea had higher DMD than OPT. Increasing DIP increased urinary N output, and increased N-retention with OPT but not Urea. Increasing DIP increased urea-N entry rate (UER) and urinary urea-N excretion (UUE) for both OPT and Urea. Gastrointestinal entry of urea-N, urea-N lost to feces and urea-N apparently used for anabolism were not different between treatments. Plasma urea concentration was greater in higher DIP diets and higher for Urea than OPT at 100% DIP.
Therefore increasing DIP level will increase N-excretion related to higher urea production and excretion in urine but may also increase diet digestibility. Most changes in N metabolism were driven by N intake; however, providing a slow release DIP source may allow for greater N retention when DIP is not limiting.
Previously we have shown a direct link between protein nutrition and starch digestion in the small intestine of beef cattle. These studies look at how protein nutrition can be optimized using alternative nitrogen sources. Future studies will link these changes directly to animal growth in hopes of optimizing nutrient utilization and minimizing nutrient excretion.
Holder, V.B., J. Tricarico, D. H. Kim, N. B. Kristensen, and D. L. Harmon. 2011. The effects of degradable nitrogen level and degradation rate on nitrogen balance and urea kinetics in Holstein steers. J. Anim. Sci. 89: (E Suppl. 1) 178.
de Godoy, M. R. C., C. E. Conway, K. R. McLeod, and D. L. Harmon. 2011. Influence of feeding a fish oil containing diet to adult lean dogs: Effects on lipid and protein metabolism, postprandial glycemia, and body weight. J. Anim. Sci. 89: (E Suppl. 1) 286.
de Godoy, M. R. C., K. R. McLeod, and D. L. Harmon. 2011. Influence of feeding a fish oil containing diet to mature overweight dogs: Effects on lipid and protein metabolism, postprandial glycemia, and body weight. J. Anim. Sci. 89: (E Suppl. 1) 286.
Foote, A. P., D. L. Harmon, K.R. Brown, J. R. Strickland, K. R. McLeod, L. P. Bush, and J. L. Klotz. 2011. Endophyte-infected tall fescue seed extract induces constriction of bovine vasculature. J. Anim. Sci. 89: (E Suppl. 1) 49.
Foote, A. P., D. L. Harmon, K. R. Brown, J. R. Strickland, K. R. McLeod, L. P. Bush, and J. L. Klotz. 2011. Constriction of bovine vasculature caused by endophyte-infected tall fescue seed extract is similar to pure ergovaline. J. Anim. Sci. (In Press)
Bohaty, R.E., M. R. C. de Godoy, K.R. McLeod, and D. L. Harmon. 2011. The effects of added sulfur amino acids, threonine, and an ideal amino acid ratio on nitrogen metabolism in mature, overweight dogs. Arch. Anim. Nutr. DOI:10.1080/1745039X.2011.629806.
Koontz, A.F., L.P. Bush, J. L. Klotz, K.R. McLeod, F.N. Schrick, and D.L. Harmon. 2011. Evaluation of a ruminally dosed tall fescue seed extract as a model for fescue toxicosis in steers. J. Anim. Sci. (In Press).
Reeder, T., G. Hibbard, K.R. McLeod and D.L. Harmon, 2011. Dietary lysine: calorie ratios and their influence on nitrogen metabolism and digestibility in moderately obese mature dogs. Am. J. Anim. Vet. Sci., 6: 45-54.
Bohnert, D. W., T. DelCurto, A. A. Clark, M. L. Merrill, S. J. Falck, and D. L. Harmon. 2011. Protein supplementation of ruminants consuming low-quality cool- or warm-season forage: differences in intake and digestibility. J. Anim. Sci. (Accepted May 20, 2011)
Foote, A. P., D. L. Harmon, J. R. Strickland, L. P. Bush and J. L. Klotz. 2011. Effect of ergot alkaloids on contractility of bovine right ruminal artery and vein. J. Anim. Sci. 89:2944-2949.
Taylor-Edwards,C.C., D.G. Burrin, K.R. McLeod, J.J. Holst, and D.L. Harmon. 2011. Glucagon-like peptide-2 (GLP-2) increases small intestinal blood flow and mucosal growth in ruminating calves. J. Dairy Sci. 94:888-898.